1. Field of the Invention
The invention relates to an optical device, in particular for an automotive vehicle, such as a lighting or signaling device.
2. Description of the Related Art
A lighting or signaling device for an automotive vehicle is known from patent application EP 1 881 263, which is equivalent to U.S. Patent Publication 2008/0019139 which is incorporated herein by reference and made a part hereof, of the applicant. The lighting device can emit a light beam “F” according to a longitudinal optical axis “A”. This lighting device comprises at least one sheet for guiding the light, at least part of which appears as a portion of a spherical segment.
The guide sheet is thus delimited, in the direction of the thickness, by two guide faces substantially parallel to each other on at least some of the sheet.
The guide sheet is delimited laterally by a front output section for the light rays and by a rear reflection section for the light. The ends of the reflection section are directly connected to the ends of the output section so as to form the outer contour of the guide sheet.
The contour of the output section for the light forms a planar arc of a circle. The guide sheet comprises an input opening for the light in the sheet.
A light source is arranged in the opening close to or in contact with the input section for the light rays.
The light source can emit light rays according to a globally radial direction around a source axis “S” which is normal to the guide sheet. More precisely, the light source can radially emit a fan of light rays at least in the direction of the reflection section.
The guide sheet is made of a transparent material whose index of refraction is higher than the index of refraction of the medium in which the lighting device is intended to be immersed, air for example. Thus, a light ray introduced into the thickness of the sheet through its input section meets the higher or lower guide faces at an angle of incidence relative to the normal “N” which is higher than a limit angle of refraction. The ray can then be completely reflected by the guide faces.
The light ray is thus guided into the thickness of the guide sheet by successive reflections between the two guide faces.
The incidental light rays which emerge at the rear are intended to be reflected by the reflection section, then the light rays thus reflected are directed towards the output section. The reflected light rays thus emerge through the output section.
The light source is an light emitting diode or “LED” known as “side emitter” which emits light rays in an essentially perpendicular direction to the source axis “S”.
The light source can also consist of an incandescent lamp, for example a halogen lamp, with an axial filament, inserted in the contour delimited by the input section. Advantageously it may be proposed in this case that a zone of the guide sheet, close to the input section, is made of glass, although the remainder of the sheet is made of plastic material molded onto this zone of glass. Such a design enables the thermal problems which the use of an incandescent light source might generate to be surmounted.
In the device described above the output section, or output face, exhibits a generally planar shape, with a general profile in the form of an arc of a circle.
A device with a guide sheet is known from patent application EP 1 992 868.
The above configurations correspond in particular to circular or annular profiles, and the guide zone near the source is close to a spherical portion.
There exists in particular a need, especially at the request of automotive manufacturers, for a light guide essentially of the type described above, which exhibits an output face having any arbitrary form, in particular a non-planar shape, extending either in a plane perpendicular to the optical axis or in a plane containing the optical axis.